Mercury tube switch



March 24, 1931. W C.;d HARTW|G 1,797,574

MERCURY TUBE SWITCH Filed Jan. 25, 1925 Patented Mar. 24, 19.31

UNITED STATES WILLIAM G. HARTWIG, OF CHICAGO, ILLINOIS MERCURY TUBE SWITCH Application led January 25, 1923.

This invention relates to mercury tube switches adapted for use in closing electric circuits in responseA to changes in temperature in the room in which the switch is located. The principal object of the invention is ,to provide a mercury tube switch coniprising means for preventing the accidental or intentional manipulation of the mercury column by vibrations or blows imparted to the mercury tube or its support. In devices of this kind as heretofore constructed, the mercury tube has been mounted in such a way that a blow imparted to the casing by which it is supported was adapted to separate the mercury column within the tube and bring about a connection or disconnection of the circuit controlled by the mercury tube, regardless of the temperature of the air surrounding the mercury column. This arti- Iicial manipulaiton of the movement of the mercury column has made it possible for unauthorized persons to tamper with the operations of automatic heating systems and it is one of the objects of the present invention to overcome this diiiiculty.

Other objects and advantages of the invention will appear more clearly from the following specification taken with the accompanying drawings in which one embodiment is illustrated.

In the drawings Fig. 1 shows a longitudinal vertical section through the mercury tube switch, the section being taken through the longitudinal center line of the device; Fig. 2 shows a front elevation of the device with vthe cover'thereof removed; Fig. 3 shows a transverse Vertical section on the line 3 3 of Fig. 1 Fig. 4 shows a transverse horizontal section on the line 4-4 of Fig. 2, and Fig. 5 shows a transverse horizontal section on the line 5-5 of Fig. 2.

The invention comprises a supporting base 10 of insulating material which is oblong in shape being provided with curved extremities. This insulating base is enclosed in a sheet metal casing 11 which is stamped to form an inclosure similar in shape to that of the insulating base, being provided with an upper wall 11EL and lateral walls 11b. The 50 upper Wall has an oblong opening 12 formed Serial No. 614,741.

therein and an annular flange 13 extending upwardly around the edges of this opening being adapted to receive the edges of the lateral. walls 14l of a sheet metal cover 14 which closes the opening 12 and forms af chamber 15 on the outer side of the base 10. Two sheetsof liber board or other insulating material 16 are mounted on the outer face of the base 10 and the ends of the base are provided with langes 1()a of reduced thickness which are adapted to be engaged by U- shaped metal clips 17. The inner arms of these clips are threaded to be engaged by screws 18 which engage apertures in the casing 11 and the cover 14 thereby securing both of these parts and the clips in rigid position with respect to the supporting base.

The outer arm 2O of the lower metal clip 17 is provided with a transverse outwardly projecting flanges 21 which extends throughf' openings 22 in the insulating sheets 16 and which is provided with an opening 23 adapted to receive the bulb 24 of the mercury tube 25. The bulb 24 is frictionally engaged by a sheet metal gripping member 26 which isv crimped around the bulb of the tube and provided with lateral flanges 27 adapted to engage notches 28 formed in the supporting flange 21 on opposite sides of the opening 23, as shown particularly in Fig. -5. The` gripping member 26 is connected at 29 to a heat transmitting plate 3() which is provided With laterally extending arms 31 having a plurality of upturned tongues 32 adapted to contact with the inner surface ot' the cover 14 so that a direct connection is estabi lished between the metallic cover 14 and the metallic gripping member surrounding the bulb 24 of the mercury tube, thus causing the mercury column to respond readily to' changes in temperature in the air surrounding the metallic cover. The arms of the supporting flange 21 are provided with tips 33 which are adapted to project between adjacent tongues 32 thereby holding the transmitting member 30 and the gripping member 26 against vertical displacements within the chamber 15.

The mercury tube 25 is provided at suitable points along its length with metallic contacts 35 and 36 which extend through the tube into the vertical opening therein to be engaged by the mercury column when it rises to suitable heights. Insulating material 37 is provided around the mercury tube at the point where the contacts 35 and 36 are connected and conductors 38 and V39 lead from these contacts to the respective binding posts 40 and 41 which extend through apertures in the insulating sheet 16 and are mounted on the insulating base in suitablev cavities provided for that purpose. The conductors 43 and 44, leading to the external circuit,pass through an opening 45 formed in the boss on the under side of the insulating base and are connected to the binding posts 40 and 41 as shown particularly in F ig. 1. in order to connect the conductors 43 and 44 and thereby close the circuit, in case the mercurytube 25 breaks, the terminal 40 e is connected to a metal clip 47 and the terminal 41 is connected to a metal clip 48. The member 48 extends transversely under the tube and comprises a longitudinal spring member 48 having a transverse arm 48h which projects beneath the tube and presses outwardly `on the under side thereof. lllhen in this position the extremity of the member 48a underlies the tip of the clip 47 but is out of contact therewith. If the tube breaks, the spring member '48*1 is permitted to move outwardly, due to the tact that the arm 48b is released, thereby causing the end of the spring member to engage the spring member 47 and close the circuit.

The metallic clip 17 at the upper end of the insulating base has an outer arm 50, similar to the arm 20 of the lower clip and this arm is provided with a transverse flange 51 which extends outwardly through openings 52 formed in the insulating sheet 16. This flange is recessed as shown at 53 to receive a bushing 54, formed of rubber or other suitable material, which is engaged by the mercury tube 25. The bushing is provided on its outer side with an annular groove 55 which engages the walls of the recess 53 on its inner side, and is engaged on its outer side by a retaining member 56, having the form illustrated particularly in Fig.v 4 where its extremities are shown as projecting inwardly at 56a to be engaged by the reversely bent arm 57 which are formed on the supporting flange 51. The annular groove 55 formed in the bushings 54 has a greater width vertically than the thickness of the flange 51 and the retaining member 56 and a loose frictional engagement is provided between the bushing and the contacting parts so that relative movement thereof is permitted. The rictional engagement of the mercury tube with the bore of the bushing 54 may also be somewhat loose in order to permit a yslight tive movement of the tube with respect to the bushing, although this may not be necessary if the bushing has movement with respect to its support. The provision of this loose frictional support for the mercury tube has been found to insure the stability of the mercury tube and the mercury column contained therein, regardless of any blows or'rvibrations which are imparted to the supporting base or the inclosing `casing and cover, so that when the mercury tube is inelosed the manipulation of the. mercury column to establish a circuit between the contacts 35 and 36 is prevented. The loose support of the lower end of the mercury column provided by the clearance between the extremities 33 of the supporting flange 21 and the lateral edges of the tongues 32' is adapted to cooperate with the loose mounting of the upper end of the tube to bring about the desired result even vwhen the bulb 24 is tightly engaged by the gripping device 26, but it may be'preferable in practice to provide a loose frictional engagement between the bulb 24 and the device 26 relying upon the bushing 54 to support the mercury tube which would then tightly engage the bore of the bushing. The means for closing the circuit upon breakage of the tube, disclosed herein, is claimed in my Patent No.V 1,567,140, granted December 29, 1925, on an application cepending herewith. y

Although I have shown and described a single embodiment of the invention for purposes of illustration, it will be understood that it may be constructed in various other forms without departing from the scope of the yappended claims.

Iclaim:

1. In aV device of the class described, a supporting base, a mercury tube, a bushing mounted on said tube and a clip connected to said base and having a rictional engagement with Said bushing to permit relative sliding movement of said 'bushing and said tube longitudinally of said base within said clip, i

2. In a device of the class described, a supporting base, a mercury tube, 'a bushing en! gaging said tube and having an4 annular groove in its outer surface and a clip engaging said groove and connected to said base, said clip being ofless thickness than the width of said groove.

3. ln a device of the class described, a supporting base, a mercury tube, a gripping member frictionally `engaging the lower end of said tube, means connected to said base andY engaging said gripping member for permitting relative sliding movement thereof with respect to said base. means frictionally engaging the upper end'of said tube, and means forming a slidable connection between s'aid4 tube and having a plurality of tongues extending therefrom, a metallic cap mounted over said tube on said base and contacting with said tongues, and a clip connected to said base and loosely engaging the space between two of said tongues.

5. In a device of the class described, a supporting base, a mercury tube, a metallic gripping member attached to said tube and having a plurality of tongues extending therefrom, and a metallic cap mounted over said tube on said base and contacting with said tongues.

6. In a device of the class described, a supporting base, a mercury tube, a metallic gripping member attached to said tube and having a plurality of tongues extending therefrom, a metallic cap mounted over said tube on said base and contacting with said tongues, and a clip attached to said base and engaging the space between two of said tongues.

7. In a device of the class described, a supporting insulating base, a pair of metallic clips having portions thereof reversely bent over the ends of said base and each having a fiange extending outwardly from said base, a mercury tube, means connected to said tube and engaging said outwardly directed flanges of said clips for supporting said tube and permitting relative movement thereof with re spect to said base, a cap mounted over said tube, and securin means engaging said cap and the reversely ent portions of the ends 0f said clips.

WILLIAM G. HARTWIG. 

